If you add organic matter to clay a bit at a time, even just topdressing, it can eventually become very workable but it will take time. Sooo, did you spray the dormants with the insecticide/fungicide or weren't they up yet? This is a process of elimination - if you sprayed the dormants and they look fine then it isn't as likely to be damage from the spray unless there's a variation in sensitivity between the plants. If the dormants weren't up and didn't get sprayed but the others did, then there's a possibility that this is damage from the spray (called phytotoxicity).
